1. Field of the Invention
This invention relates to an audio signal reproducing apparatus and more particularly to an apparatus for reproducing a recorded signal from a recording medium on which some of audio signals of a plurality of kinds are recorded.
2. Description of the Related Art
The video tape recorder (VTR) of the camera-integrated type has recently come to be arranged to record and reproduce sounds in a stereophonic state. Even the VTR of the conventional kind recording a monaural audio signal by frequency-modulating it with a carrier wave of 1.5 MHz has come to be arranged to record, with the frequency modulation carrier wave of 1.5 MHz, a sum signal obtained from L (left) and R (right) channels and further to record a difference signal between the L and R channel signals by newly providing a frequency modulation carrier wave of 1.7 MHz.
In cases where different audio signals are to be recorded separately in the L and R channels (for example, the Japanese language in the L channel and the English language in the R channel) as main-and-sub audio signals, the VTR which is arranged to record the stereophonic audio signals by the above-stated sum/difference signal recording method is required to find whether recorded signals are stereophonic audio signals or main-and-sub audio signals and to switch its signal processing mode from one mode over to another by determining whether or not these signals should be allowed to pass through a matrix circuit.
It is, however, troublesome to manually perform the above-stated switch-over of processes. Besides, erroneous switch-over would greatly degrade the quality of reproduced sounds. To avoid the error, therefore, it has been desired to automatically switch one processing mode over to another. For this purpose, identification data which indicates the kinds of the audio signals must be somehow recorded on the recording medium and the above-stated switch-over must be performed according to the identification data.
Generally, however, a real-time analog audio signal does not include any surplus part. It has been, therefore, difficult to add such identification data to the audio signal. Further, it hinders high density recording to record and reproduce the identification data in addition to the audio signal. Besides, it requires use of discrete recording/reproducing means.
To solve this problem, it is conceivable to multiplex the identification data and the audio signal together. However, since the audio signal does not have any surplus part, the multiplexed identification data tends to be erroneously detected. Such erroneous detection would cause a large noise in the reproduced audio signal.